The aim of this proposal is to establish a rigorous, well-structured, closely-supervised training program that will promote the development of the technical and intellectual skills necessary for success as an independent physician-scientist. This will be accomplished in the laboratory of Dr. Steven M. Albelda through a focused project allowing the candidate to pursue his interest in the basic signaling mechanisms underlying pulmonary vascular responses to inflammation and repair. Research Program: The vascular adhesion molecule Platelet Endothelial Cell Adhesion Molecule-1 (PECAM-1) is expressed at very high levels on endothelial cells (EC). Although PECAM-1 has been implicated in specific endothelial functions such as angiogenesis, vasculogenesis, and neutrophil transmigration, the mechanisms responsible for these activities are unknown. PECAM-1 has recently been shown to undergo tyrosine phosphorylation after ligation. In non-endothelial cells, this event is associated with binding of the tyrosine phosphatase and adaptor protein SHP- 2. The central hypothesis of this proposal is that PECAM-1 regulates endothelial function through specific tyrosine-dependent and tyrosine-independent interactions with select signal transducing intermediates. This hypothesis will be tested using molecular genetic and dominant-negative approaches aimed at linking PECAM-1 signal transduction with two specific measures of PECAM-regulated endothelial function and signaling: cell migration and calcium flux. Specifically, the applicant will 1) determine which regions (and specific amino acid residues) of the PECAM-1 cytoplasmic domain are necessary for tyrosine-dependent PECAM-1 signaling and determine if these are the same regions needed to bind to SHP-2, 2) determine if SHP-2 binding is functionally important, and if so, whether the phosphatase and/or the protein interaction adaptor domains are required, and 3) identify and characterize alternate tyrosine-dependent and tyrosine-independent PECAM-1 signaling pathways. Training Plan: In addition to the research proposal, an important component of the Candidate's training will be the completion of a formal Ph.D degree in Cell and Molecular Biology. Having successfully completed all laboratory rotation, coursework, and preliminary examination requirements over the past two years, the Candidate has recently entered the thesis period and will be closely supervised by a formal graduate committee. The second aspect of the Candidate's training will be his continued participation in the Pulmonary and Critical Care Research Training Program that consists of a mentoring committee and a clinical and basic science curriculum composed of graduate seminar series, journal clubs, select didactic courses, and a clinical seminar series. Common to both programs is a university-wide seminar series on the ethics of research. This training plan will continue throughout the duration of this grant and facilitate supervision of the candidate's transition to independence after completion of the formal Ph.D. degree.